HIV-1 host cell factors: a saturation screen for human chromosomes 4, 6, 21 and X. There is intense interest in identifying cellular host cell factors that modulate the life cycle of HIV-1. These factors can be classified as restriction factors that inhibit infection and permissive factors that aid the infection process. The study of these factors will aid in our understanding of viral and host cell interactions and to identify novel cellular drug targets. Since present drug therapies are based on targeting viral proteins, and the high mutation rate of HIV is able to generate resistance to these antiviral drugs, cellular proteins may constitute targets in which resistance is harder to generate. Various strategies to identify these proteins have been used. Here we propose an approach for the identification of host cell factors for the early life cycle of HIV. We aim to do a saturating insertional mutagenesis screen that will sample 1/5 of the human genome for host cell factor genes. We will achieve this aim using cells that have monosomies of chromosomes 4, 6, 21 and X. We will develop an insertional vector that disrupts gene function and select cells infected with this mutagenic vector for resistance to HIV-1 infection using an HIV-1 vector that is toxic on infection. Insertions into chromosome 4, 6, 21 and X will be identified through sequencing of DNA flanking the mutagenic vector. At the conclusion of this study we will have at least 2-3 verified host cell factors and the point in the lifecycle at which they are utilized. We will also have in hand a valuable resource - a knockout cell line of the host cell factor. This will enable structure-function relationships of the protein and the virus in future studies. These host cell factors may constitute novel targets for small drug molecules to combat HIV-1 and AIDS. PUBLIC HEALTH RELEVANCE: HIV-1 host cell factors: a saturation screen for human chromosomes 4, 6, 21 and X. HIV-1 relies on host cell proteins to complete its replication cycle. Identification of these factors is important since they are potential targets for the development of drugs to combat HIV-1 infection. In this study we aim to interrogate 1/5 the human genome in a pilot study to discover some host cell factors required by HIV-1 for infection.